Impression Evidence · PDF fileKathy Mirakovits, FSEC 3 Types of Impression Evidence...

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Transcript of Impression Evidence · PDF fileKathy Mirakovits, FSEC 3 Types of Impression Evidence...

  • Kathy Mirakovits, FSEC 1

    Impression Evidence Shoeprints

  • Kathy Mirakovits, FSEC 2

    Footwear and Tire Treads

    Impression-one object makes physical contact with another leaving some of its physical characteristics on the recipient

    Soft or pliable materials leave three dimensional impressionsputty, mud, concrete, soft dirt

    Hard surfaces have two dimensional impressionsdirt, dust, blood, ink

  • Kathy Mirakovits, FSEC 3

    Types of Impression Evidence Fingerprints Tire tracks

    Footprints Firing pin impressions

  • Kathy Mirakovits, FSEC 4

    Footwear Impressions

    Footwear impressions maybe left at crime scenes, and in entry and exit locations of scenes

    Footwear evidence may be overlooked due to: May be nearly invisible On uneven ground Trampled by other footwear Footwear evidence is misunderstood or undervalued

    by police, detectives, judges, and juries Footwear evidence can be fragilemust use

    photography and make casts of impressions

  • Kathy Mirakovits, FSEC 5

    Individual v. Class Evidence

    New shoes without wear: generally class evidence With wear and tear: imperfections, alterations and

    random markings cause shoes to individualize Abundance of unique details allows a competent

    examiner to conclude the impression came from a particular shoe

    No agreed upon standards for: -number of points of identification

    -type or quality of the ID points From a good impressionsize and type of shoe Manufacturing imperfections add discrimination

  • Kathy Mirakovits, FSEC 6

    Athletic Shoe With Unique Patterns

    wear patterns highlighted

    imbedded materials highlighted

  • Kathy Mirakovits, FSEC 7

    Footwear Impressions

    Formed by a shoe deforming a surface May leave three dimensional impressions Trace evidence may be transferred from shoe to

    surface (positive impression) Trace evidence may be transferred from surface

    to shoe (negative impression) Static electricity build up can increase transfer of


  • Kathy Mirakovits, FSEC 8

    Preservation of Footwear Impressions

    Photograph footprints Photograph footprint with ruler or measuring tool

    for court testimony In two dimensional footprint cases, photo will be

    used for comparison Three dimensional footprints are casted: using

    material that fills impression and then hardens to capture impression image

  • Kathy Mirakovits, FSEC 9

    Casting Footwear

    The primary material of choice to cast footprints is dental stone due to its hardness and ability to capture detail

    Captures detail of footprint to a much greater extent than other materials, such as plaster of paris